Pressure-sensitive adhesive layer-attached polarizing film and image display

ABSTRACT

A pressure-sensitive adhesive layer-attached polarizing film of the invention includes: a polarizing film; and a pressure-sensitive adhesive layer provided on the polarizing film, wherein the polarizing film includes a polarizer and a transparent protective film provided on only one side of the polarizer, the pressure-sensitive adhesive layer is provided on a side of the polarizer where the transparent protective film is absent, and the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive composition containing a (meth)acryl-based polymer (A) and an alkali metal salt (B). The pressure-sensitive adhesive layer-attached polarizing film has a pressure-sensitive adhesive layer with an antistatic function and satisfactory durability and whose optical properties are less likely to be degraded.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/069,004 filed on Mar. 14, 2016, which is a divisional of U.S. patentapplication Ser. No. 13/479,406 filed on May 24, 2012 and issued as U.S.Pat. No. 9,557,450 on Jan. 31, 2017, which claims priority of JapanesePatent Application No. 2011-118334 filed on May 26, 2011. The entirecontent of each of the foregoing is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a pressure-sensitive adhesive layer-attachedpolarizing film having a polarizing film and a pressure-sensitiveadhesive layer provided on the polarizing film. The present inventionalso relates to an image display, such as a liquid crystal display, anorganic electroluminescence (EL) display, or a plasma display panel(PDP), produced using the pressure-sensitive adhesive layer-attachedpolarizing film.

Description of the Related Art

The image-forming system of liquid crystal displays or the like requirespolarizing elements to be placed on both sides of a liquid crystal cell,and generally polarizing films are bonded thereto. When the polarizingfilms are bonded to a liquid crystal cell, pressure-sensitive adhesivesare generally used. Bonding between a polarizing film and a liquidcrystal cell is generally performed with a pressure-sensitive adhesivein order to reduce optical loss. In such a case, a pressure-sensitiveadhesive layer-attached polarizing film including a polarizing film anda pressure-sensitive adhesive layer previously formed on one side of thepolarizing film is generally used, because it has some advantages suchas no need for a drying process to fix the polarizing film. In general,a release film is attached to the pressure-sensitive adhesive layer ofthe pressure-sensitive adhesive layer-attached polarizing film.

During the manufacture of a liquid crystal display, thepressure-sensitive adhesive layer-attached polarizing film is bonded toa liquid crystal cell. In this process, static electricity is generatedwhen the release film is peeled off from the pressure-sensitive adhesivelayer of the pressure-sensitive adhesive layer-attached polarizing film.The static electricity generated in this manner may affect theorientation of the liquid crystal in the liquid crystal display to causea failure. The static electricity may also cause display unevenness whenthe liquid crystal display operates. For example, the static generationcan be suppressed when an antistatic layer is formed on the outersurface of the polarizing film, but its effect is not high, and there isa problem in which static generation cannot be fundamentally prevented.To suppress static generation in a fundamental position, therefore, thepressure-sensitive adhesive layer is required to have an antistaticfunction. Concerning means for providing an antistatic function to apressure-sensitive adhesive layer, for example, it is proposed that anionic compound should be added to a pressure-sensitive adhesive used toform a pressure-sensitive adhesive layer (Patent Documents 1 and 4).Concerning an acrylic pressure-sensitive adhesive for use in forming apolarizing film, Patent Document 1 discloses the addition of a lithiumsalt to such an adhesive, Patent Document 2 the addition of at least oneof an alkali metal salt and an alkaline-earth metal salt to such anadhesive, Patent Document 3 the addition of an ionic compound having anorganic cation and being solid at room temperature to such an adhesive,and Patent Document 4 the addition of an ionic solid containing animidazolium cation and an inorganic anion to such an adhesive. There isalso proposed a method of forming an antistatic layer between apolarizing film and a pressure-sensitive adhesive layer using a binderof a conductive polymer such as polythiophene. The pressure-sensitiveadhesive layer-attached polarizing film is also required to havedurability in the adhering state.

-   Patent Document 1: JP-A No. 2010-189489-   Patent Document 2: JP-A No. 2010-065217-   Patent Document 3: JP-A No. 2010-066756-   Patent Document 4: JP-A No. 2009-251281-   Patent Document 5: JP-A No. 2003-246874

SUMMARY OF THE INVENTION

According to Patent Documents 1 to 4, a pressure-sensitive adhesivelayer formed using a pressure-sensitive adhesive composition containingan ionic compound is applied to a polarizing film so that an antistaticfunction is provided to the film. The polarizing films disclosed inPatent Documents 1 to 4 all include a polarizer and protective materialssuch as transparent protective films provided on both sides of thepolarizer.

On the other hand, in some cases, another pressure-sensitive adhesivelayer-attached polarizing film may be used, which includes a polarizer,a transparent protective film provided on only one side of thepolarizer, and a pressure-sensitive adhesive layer provided on the otherside of the polarizer, with no transparent protective film provided onthe other side. The pressure-sensitive adhesive layer-attachedpolarizing film, which has a transparent protective film provided ononly one side, makes it possible to reduce the cost of one layer oftransparent protective film in contrast to the film having transparentprotective films on both sides. Unfortunately, the pressure-sensitiveadhesive layer-attached polarizing film has a problem in which when thepressure-sensitive adhesive layer contains an ionic compound forproviding an antistatic function, the ionic compound in thepressure-sensitive adhesive layer can significantly affect thepolarizer, so that, for example, when an ionic liquid or solid is usedas the ionic compound, it may deteriorate the polarizer to significantlydegrade the optical properties after a humidification test.

Also when a layer containing a conductive polymer such as polythiopheneis provided between a polarizing film and a pressure-sensitive adhesivelayer according to Patent Document 5, the polarizer and the opticalproperties will be deteriorated and degraded.

An object of the present invention is to provide a pressure-sensitiveadhesive layer-attached polarizing film which has a pressure-sensitiveadhesive layer with an antistatic function and satisfactory durabilityand whose optical properties are less likely to be degraded.

Another object of the present invention is to provide an image displayproduced using such a pressure-sensitive adhesive layer-attachedpolarizing film.

As a result of investigations for solving the problems, the inventorshave found the pressure-sensitive adhesive layer-attached polarizingfilm described below and have completed the present invention.

The present invention relates to a pressure-sensitive adhesivelayer-attached polarizing film, including:

a polarizing film; and

a pressure-sensitive adhesive layer provided on the polarizing film,wherein

the polarizing film includes a polarizer and a transparent protectivefilm provided on only one side of the polarizer,

the pressure-sensitive adhesive layer is provided on a side of thepolarizer where the transparent protective film is absent, and

the pressure-sensitive adhesive layer is made of a pressure-sensitiveadhesive composition containing a (meth)acryl-based polymer (A) and analkali metal salt (B).

In the pressure-sensitive adhesive layer-attached polarizing film, thealkali metal salt (B) is preferably a lithium salt.

In the pressure-sensitive adhesive layer-attached polarizing film, it ispreferable to includes 0.0001 to 5 parts by weight of the alkali metalsalt (B) based on 100 parts by weight of the (meth)acryl-based polymer(A).

In the pressure-sensitive adhesive layer-attached polarizing film, thepolarizer may have a thickness of 10 μm or less. As the polarizer havinga thickness of 10 μm or less, it is preferable to use a polarizing layerin the form of a continuous web, and the polarizing layer includes apolyvinyl alcohol-based resin containing an oriented dichroic materialand is a product obtained by a two-stage stretching process includingsubjecting a laminate to auxiliary in-air stretching and subjecting thelaminate to stretching in an aqueous boric acid solution, wherein thelaminate includes a thermoplastic resin substrate and a polyvinylalcohol-based resin layer formed on the substrate.

In the pressure-sensitive adhesive layer-attached polarizing film, it ispreferable to use the (meth)acryl-based polymer (A) including an alkyl(meth)acrylate monomer unit and a hydroxyl group-containing monomerunit.

In the pressure-sensitive adhesive layer-attached polarizing film, it ispreferable to use the (meth)acryl-based polymer (A) including an alkyl(meth)acrylate monomer unit and a carboxyl group-containing monomerunit.

The pressure-sensitive adhesive composition for an optical film furthermay include a crosslinking agent (C). In the pressure-sensitive adhesivecomposition for an optical film, it is preferable to include 0.01 to 20parts by weight of the crosslinking agent (C) based on 100 parts byweight of the (meth)acryl-based polymer (A). The crosslinking agent (C)is preferably at least one selected from an isocyanate compound and aperoxide.

The pressure-sensitive adhesive layer-attached polarizing film mayfurther include 0.001 to 5 parts by weight of a silane coupling agent(D) based on 100 parts by weight of the (meth)acryl-based polymer (A).

The pressure-sensitive adhesive layer-attached polarizing film mayfurther include 0.001 to 10 parts by weight of a polyether-modifiedsilicone compound based on 100 parts by weight of the (meth)acryl-basedpolymer (A).

In the pressure-sensitive adhesive layer-attached polarizing film, the(meth)acryl-based polymer (A) preferably has a weight average molecularweight of 500,000 to 3,000,000.

The pressure-sensitive adhesive layer-attached polarizing film mayfurther include an adhesion-facilitating layer that is provided betweenthe polarizing film and the pressure-sensitive adhesive layer.

The present invention also relates to an image display, including atleast one piece of the pressure-sensitive adhesive layer-attachedoptical film.

EFFECTS OF THE INVENTION

If an ionic compound is added to a pressure-sensitive adhesive producedusing an acryl-based polymer as a base polymer, an antistatic functioncan be provided to the pressure-sensitive adhesive. It is consideredthat in this case, the ionic compound can bleed out to the surface ofthe pressure-sensitive adhesive layer, so that the antistatic functioncan be efficiently produced. On the other hand, if the ionic compoundcomes into contact with a polarizer, its optical properties such as thedegree of polarization may be degraded.

The pressure-sensitive adhesive composition used to form thepressure-sensitive adhesive layer of the pressure-sensitive adhesivelayer-attached polarizing film of the present invention contains a(meth)acryl-based polymer (A)and an alkali metal salt (B) capable ofproviding an antistatic function, and the pressure-sensitive adhesivelayer made of the pressure-sensitive adhesive composition has a goodantistatic function. It has also been found that when the alkali metalsalt (B) is used according to the present invention, an antistaticfunction can be provided without degradation of a polarizer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS BRIEF DESCRIPTION OFTHE DRAWINGS

FIG. 1 is a cross-sectional view showing a pressure-sensitive adhesivelayer-attached polarizing film according to the invention.

FIG. 2 is a cross-sectional view showing a pressure-sensitive adhesivelayer-attached polarizing film according to the invention.

FIG. 3 is a cross-sectional view showing a liquid crystal displayaccording to the invention.

The pressure-sensitive adhesive composition forming a pressure-sensitiveadhesive of the pressure-sensitive adhesive layer-attached polarizingfilm of the present invention contains a (meth)acryl-based polymer (A)as a base polymer. The (meth)acryl-based polymer (A) includes an alkyl(meth)acrylate monomer unit as a main component. The term“(meth)acrylate” refers to acrylate and/or methacrylate, and “(meth)” isused in the same meaning in the description.

The alkyl (meth)acrylate used to form the main skeleton of the(meth)acrylic polymer (A) may have a straight- or branched-chain alkylgroup of 1 to 18 carbon atoms. Examples of such an alkyl group includemethyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl,cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl,dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl,heptadecyl, and octadecyl groups. These may be used singly or in anycombination. The average number of carbon atoms in the alkyl group ispreferably from 3 to 9.

An aromatic ring-containing alkyl (meth)acrylate such as phenoxyethyl(meth)acrylate or benzyl (meth)acrylate may also be used in view ofcontrol of adhesive properties, durability, retardation, refractiveindex, or the like. A polymer obtained by polymerizing the aromaticring-containing alkyl (meth)acrylate may be used in a mixture with anyof the above examples of the (meth)acryl-based polymer. In view oftransparency, however, a copolymer obtained by polymerizing the aromaticring-containing alkyl (meth)acrylate and the above alkyl (meth)acrylateis preferably used.

The content of the aromatic ring-containing alkyl (meth)acrylatecomponent in the (meth)acryl-based polymer (A) may be 50% by weight orless based on the content (100% by weight) of all the monomer componentsof the (meth)acryl-based polymer (A). The content of the aromaticring-containing alkyl (meth)acrylate is preferably from 1 to 35% byweight, more preferably from 1 to 20% by weight, even more preferablyfrom 7 to 18% by weight, still more preferably from 10 to 16% by weight.

In order to improve tackiness or heat resistance, one or morecopolymerizable monomers having an unsaturated double bond-containingpolymerizable functional group such as a (meth)acryloyl group or a vinylgroup may be introduced into the (meth)acryl-based polymer (A) bycopolymerization. Examples of such copolymerizable monomers includehydroxyl group-containing monomers such as 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate,10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and(4-hydroxymethylcyclohexyl)-methyl acrylate; carboxyl group-containingmonomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate,carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid,and crotonic acid; acid anhydride group-containing monomers such asmaleic anhydride and itaconic anhydride; caprolactone adducts of acrylicacid; sulfonic acid group-containing monomers such as styrenesulfonicacid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonicacid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate,and (meth) acryloyloxynaphthalenesulfonic acid; and phosphategroup-containing monomers such as 2-hydroxyethylacryloyl phosphate.

Examples of such a monomer for modification also include

(N-substituted) amide monomers such as (meth)acrylamide,N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide,N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide;alkylaminoalkyl (meth)acrylate monomers such as aminoethyl(meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, andtert-butylaminoethyl (meth) acrylate; alkoxyalkyl (meth)acrylatemonomers such as methoxyethyl (meth)acrylate and ethoxyethyl(meth)acrylate; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyoctamethylenesuccinimide, and N-acryloylmorpholine;maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide,N-laurylmaleimide, and N-phenylmaleimide; and itaconimide monomers suchas N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide,N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide,and N-laurylitaconimide.

Examples of modification monomers that may also be used include vinylmonomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone,methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine,vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole,vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene,a-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such asacrylonitrile and methacrylonitrile; epoxy group-containing acrylicmonomers such as glycidyl (meth)acrylate; glycol acrylic ester monomerssuch as polyethylene glycol (meth)acrylate, polypropylene glycol(meth)acrylate, methoxyethylene glycol (meth)acrylate, andmethoxypolypropylene glycol (meth)acrylate; and acrylate ester monomerssuch as tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate,silicone (meth)acrylate, and 2-methoxyethyl acrylate. Examples alsoinclude isoprene, butadiene, isobutylene, and vinyl ether.

Besides the above, a silicon atom-containing silane monomer may beexemplified as the copolymerizable monomer. Examples of the silanemonomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane,vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane,4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane,8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane,acryloyloxydecyltrimethoxysilane, methacryloyloxydecyltriethoxysilane,and acryloyloxydecyltriethoxysilane.

Copolymerizable monomers that may be used also include polyfunctionalmonomers having two or more unsaturated double bonds such as(meth)acryloyl groups or vinyl groups, which include (meth)acrylateesters of polyhydric alcohols, such as tripropylene glycoldi(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate,neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, and caprolactone-modified dipentaerythritolhexa(meth)acrylate; and compounds having a polyester, epoxy or urethaneskeleton to which two or more unsaturated double bonds are added in theform of functional groups such as (meth)acryloyl groups or vinyl groupsin the same manner as the monomer component, such as polyester(meth)acrylates, epoxy (meth)acrylates and urethane (meth) acrylates.

Concerning the weight ratios of all monomer components, the alkyl(meth)acrylate should be a main component of the (meth)acryl-basedpolymer (A), and the content of the copolymerizable monomer used to formthe (meth)acryl-based polymer (A) is preferably, but not limited to, 0to about 20%, more preferably about 0.1 to about 15%, even morepreferably about 0.1 to about 10%, based on the total weight of allmonomer components.

Among these copolymerizable monomers, hydroxyl group-containing monomersor carboxyl group-containing monomers are preferably used in view oftackiness or durability. The hydroxyl group-containing monomer may beused in combination with the carboxyl group-containing monomer. When thepressure-sensitive adhesive composition contains a crosslinking agent,these copolymerizable monomers can serve as a reactive site with thecrosslinking agent. Such hydroxyl group-containing monomers or carboxylgroup-containing monomers are highly reactive with intermolecularcrosslinking agents and therefore are preferably used to improve thecohesiveness or heat resistance of the resulting pressure-sensitiveadhesive layer. Hydroxyl group-containing monomers are preferred interms of reworkability, and carboxyl group-containing monomers arepreferred in terms of achieving both durability and reworkability.

When a hydroxyl group-containing monomer is added as a copolymerizablemonomer, its content is preferably from 0.01 to 15% by weight, morepreferably from 0.03 to 10% by weight, even more preferably from 0.05 to7% by weight. When a carboxyl group-containing monomer is added as acopolymerizable monomer, its content is preferably from 0.05 to 10% byweight, more preferably from 0.1 to 8% by weight, even more preferablyfrom 0.2 to 6% by weight.

In an embodiment of the present invention, the (meth)acryl-based polymer(A) used generally has a weight average molecular weight in the range of500,000 to 3,000,000. In view of durability, particularly in view ofheat resistance, the weight average molecular weight of the polymer (A)used is preferably from 700,000 to 2,700,000, more preferably from800,000 to 2,500,000. If the weight average molecular weight is lessthan 500,000, it is not preferred in view of heat resistance. If aweight average molecular weight is more than 3,000,000, it is notpreferred because a large amount of a dilution solvent may be necessaryfor control of coating viscosity, which may increase cost. The weightaverage molecular weight refers to the value obtained by measurement bygel permeation chromatography (GPC) and conversion of the measured valueinto the polystyrene-equivalent value.

For the production of the (meth)acrylic polymer (A), any appropriatemethod may be selected from known production methods such as solutionpolymerization, bulk polymerization, emulsion polymerization, andvarious radical polymerization methods. The resulting (meth)acrylicpolymer (A) may be any type of copolymer such as a random copolymer, ablock copolymer and a graft copolymer.

In a solution polymerization process, for example, ethyl acetate,toluene or the like is used as a polymerization solvent. In a specificsolution polymerization process, for example, the reaction is performedunder a stream of inert gas such as nitrogen at a temperature of about50 to about 70° C. for about 5 to about 30 hours in the presence of apolymerization initiator.

Any appropriate polymerization initiator, chain transfer agent,emulsifying agent and so on may be selected and used for radicalpolymerization. The weight average molecular weight of the (meth)acrylicpolymer (A) may be controlled by the reaction conditions including theamount of addition of the polymerization initiator or the chain transferagent and monomers concentration. The amount of the addition may becontrolled as appropriate depending on the type of these materials.

Examples of the polymerization initiator include, but are not limitedto, azo initiators such as 2,2′-azobisisobutylonitrile,2,2′-azobis(2-amidinopropane)dihydrochloride,2,2′-azobis[2-(5-methyl-2-imidazoline-2-yl)propane]dihydrochloride,2,2′-azobis(2-methylpropionamidine)disulfate,2,2′-azobis(N,N′-dimethyleneisobutylamidine), and2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057,manufactured by Wako Pure Chemical Industries, Ltd.); persulfates suchas potassium persulfate and ammonium persulfate; peroxide initiatorssuch as di(2-ethylhexyl)peroxydicarbonate,di(4-tert-butylcyclohexyl)peroxydicarbonate,di-sec-butylperoxydicarbonate, tert-butylperoxyneodecanoate,tert-hexylperoxypivalate, tert-butylperoxypivalate, dilauroyl peroxide,di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide,tert-butylperoxyisobutylate, 1,1-di(tert-hexylperoxy)cyclohexane,tert-butylhydroperoxide, and hydrogen peroxide; and redox systeminitiators of a combination of a peroxide and a reducing agent, such asa combination of a persulfate and sodium hydrogen sulfite and acombination of a peroxide and sodium ascorbate.

One of the above polymerization initiators may be used alone, or two ormore thereof may be used in a mixture. The total content of thepolymerization initiator is preferably from about 0.005 to 1 part byweight, more preferably from about 0.02 to about 0.5 parts by weight,based on 100 parts by weight of the monomer.

For example, when 2,2′-azobisisobutyronitrile is used as apolymerization initiator for the production of the (meth)acrylic polymerwith the above weight average molecular weight, the polymerizationinitiator is preferably used in a content of from about 0.06 to 0.2parts by weight, more preferably of from about 0.08 to 0.175 parts byweight, based on 100 parts by weight of the total content of the monomercomponents.

Examples of the chain transfer agent include lauryl mercaptan, glycidylmercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid,2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. One of thesechain transfer agents may be used alone, or two or more thereof may beused in a mixture. The total content of the chain transfer agent ispreferably 0.1 parts by weight or less, based on 100 parts by weight ofthe total content of the monomer components.

Examples of the emulsifier used in emulsion polymerization includeanionic emulsifiers such as sodium lauryl sulfate, ammonium laurylsulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkylether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate;and nonionic emulsifiers such as polyoxyethylene alkyl ether,polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester,and polyoxyethylene-polyoxypropylene block polymers. These emulsifiersmay be used alone, or two or more thereof may be used in combination.

The emulsifier may be a reactive emulsifier. Examples of such anemulsifier having an introduced radical-polymerizable functional groupsuch as a propenyl group and an allyl ether group include Aqualon HS-10,HS-20, KH-10, BC-05, BC-10, and BC-(each manufactured by Dai-ichi KogyoSeiyaku Co., Ltd.) and Adekaria Soap SE1ON (manufactured by Asahi DenkaKogyo K.K.). The reactive emulsifier is preferred, because afterpolymerization, it can be incorporated into a polymer chain to improvewater resistance. Based on 100 parts by weight of the total monomercomponent, the emulsifier is preferably used in a content of 0.3 to 5parts by weight, more preferably of 0.5 to 1 parts by weight, in view ofpolymerization stability or mechanical stability.

In addition to (A) the (meth)acryl-based polymer, the pressure-sensitiveadhesive composition of the present invention contains (B) an alkalimetal salt. A single alkali metal salt (B) may be used, or two or morealkali metal salts (B) may be used in combination. Any of organic andinorganic salts of alkali metals may be used as the alkali metal salt.

The cation moiety of the alkali metal salt (B) includes an alkali metalion, which may be any of lithium, sodium, and potassium ions. Amongthese alkali metal ions, lithium ion is particularly preferred.

The anion moiety of the alkali metal salt (B) may include an organicmaterial or an inorganic material. Examples of the anion moiety that maybe used to form the organic salt include CH₃COO^(—), CF₃COO^(—), CH₃SO₃^(—), (CF₃So₂)₂N^(—), (CF₃SO₂)₃C^(—), C₄F₉SO₃ ^(—), (C₂F₅SO₂)₂N^(—),C₃F₇COO^(—), (CF₃SO₂) (CF₃CO)N^(—), ^(—)O₃S (CF₂)₃SO₃ ^(—), PF₆ ^(—),and CO₃ ^(2—). In particular, a fluorine atom-containing anion moiety ispreferably used because it can form an ionic compound with good ionicdissociation properties. Examples of the anion moiety that may be usedto form the inorganic salt include Cl^(—), Br^(—), I^(—), AlCl₄ ^(—),Al₂Cl₇ ^(—), BF₄ ^(—), PF₆ ^(—), ClO₄ ^(—), NO₃ ^(—), AsF₆ ^(—), SbF₆^(—), NbF₆ ^(—), TaF₆ ^(—), and (CN)₂N^(—). The anion moiety ispreferably (perfluoroalkylsulfonyl)imide such as (CF₃SO₂)₂N^(—) or(C₂F₅SO₂)₂N^(—), in particular, preferably (trifluoromethanesulfonyl)imide such as (CF₃SO₂)₂N^(—).

Examples of organic salts of alkali metals include sodium acetate,sodium alginate, sodium lignosulfonate, sodium toluenesulfonate,LiCF₃SO₃, Li (CF₃SO₂)₂N, Li (CF₃SO₂)₂N, Li (C₂F₅SO₂)₂N, Li (C₄F₉SO₂)₂N,Li (CF₃SO₂)₃C, KO₃S (CF₂)₃SO₃K, and LiO₃S (CF₂) ₃SO₃K. Among them,LiCF₃SO₃, Li (CF₃SO₂)₂N, Li (C₂F₅SO₂)₂N, Li (C₄F₉SO₂)₂N, Li (CF₃SO₂)₃C,and the like are preferred, fluorine-containing lithium imide salts suchas Li (CF₃SO₂)₂N, Li (C₂F₅SO₂)₂N, and Li (C₄F₉SO₂)₂N are more preferred,and a (perfluoroalkylsulfonyl)imide lithium salt is particularlypreferred.

Examples of inorganic salts of alkali metals include lithium perchlorateand lithium iodide.

The content of the alkali metal salt (B) in the pressure-sensitiveadhesive composition of the present invention is preferably from 0.0001to 5 parts by weight based on 100 parts by weight of the(meth)acryl-based polymer (A). If the content of alkali metal salt (B)is less than 0.0001 parts by weight, the effect of improving antistaticperformance may be insufficient. The content of the alkali metal salt(B) is preferably 0.01 parts by weight or more, more preferably 0.1parts by weight or more. On the other hand, if the content of the alkalimetal salt (B) is more than 5 parts by weight, durability may beinsufficient. The content of the alkali metal salt (B) is preferably 3parts by weight or less, more preferably 1 part by weight or less. Thecontent of the alkali metal salt (B) can be set in a preferred range,taking into account the above upper and lower limits.

The pressure-sensitive adhesive composition of the present inventionalso includes a crosslinking agent (C). An organic crosslinking agent ora polyfunctional metal chelate may also be used as the crosslinkingagent (C). Examples of the organic crosslinking agent include anisocyanate crosslinking agent, an epoxy crosslinking agents, a peroxidecrosslinking agents and an imine crosslinking agents. The polyfunctionalmetal chelate may include a polyvalent metal and an organic compoundthat is covalently or coordinately bonded to the metal. Examples of thepolyvalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca,Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. The organic compound has acovalent or coordinate bond-forming atom such as an oxygen atom.Examples of the organic compound include alkyl esters, alcoholcompounds, carboxylic acid compounds, ether compounds, and ketonecompounds.

The crosslinking agent (C) to be used is preferably selected from anisocyanate crosslinking agent and/or a peroxide crosslinking agent.Examples of such a compound for the isocyanate crosslinking agentinclude isocyanate monomers such as tolylene diisocyanate,chlorophenylene diisocyanate, tetramethylene diisocyanate, xylylenediisocyanate, diphenylmethane diisocyanate, and hydrogenateddiphenylmethane diisocyanate, and isocyanate compounds produced byadding any of these isocyanate monomers to trimethylolpropane or thelike; and urethane prepolymer type isocyanates produced by the additionreaction of isocyanurate compounds, burette type compounds, or polyetherpolyols, polyester polyols, acrylic polyols, polybutadiene polyols,polyisoprene polyols, or the like. Particularly preferred is apolyisocyanate compound such as one selected from the group consistingof hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, andisophorone diisocyanate, or a derivative thereof. Examples of oneselected from the group consisting of hexamethylene diisocyanate,hydrogenated xylylene diisocyanate, and isophorone diisocyanate, or aderivative thereof include hexamethylene diisocyanate, hydrogenatedxylylene diisocyanate, isophorone diisocyanate, polyol-modifiedhexamethylene diisocyanate, polyol-modified hydrogenated xylylenediisocyanate, trimer-type hydrogenated xylylene diisocyanate, andpolyol-modified isophorone diisocyanate. The listed polyisocyanatecompounds are preferred, because their reaction with a hydroxyl groupquickly proceeds as if an acid or a base contained in the polymer actsas a catalyst, which particularly contributes to the rapidness of thecrosslinking.

Any peroxide capable of generating active radical species by heating orphotoirradiation and promoting the crosslinking of the base polymer inthe pressure-sensitive adhesive composition may be appropriately used.In view of workability and stability, a peroxide with a one-minutehalf-life temperature of 80° C. to 160° C. is preferably used, and aperoxide with a one-minute half-life temperature of 90° C. to 140° C. ismore preferably used.

Examples of the peroxide for use in the present invention includedi(2-ethylhexyl) peroxydicarbonate (one-minute half-life temperature:90.6° C.), di(4-tert-butylcyclohexyl) peroxydicarbonate (one-minutehalf-life temperature: 92.1° C.), di-sec-butyl peroxydicarbonate(one-minute half-life temperature: 92.4° C.), tert-butylperoxyneodecanoate (one-minute half-life temperature: 103.5° C.),tert-hexyl peroxypivalate (one-minute half-life temperature: 109.1° C.),tert-butyl peroxypivalate (one-minute half-life temperature: 110.3° C.),dilauroyl peroxide (one-minute half-life temperature: 116.4° C.),di-n-octanoylperoxide (one-minute half-life temperature: 117.4° C.),1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate (one-minute half-lifetemperature: 124.3° C.), di(4-methylbenzoyl) peroxide (one-minutehalf-life temperature: 128.2° C.), dibenzoyl peroxide (one-minutehalf-life temperature: 130.0° C.), tert-butyl peroxyisobutylate(one-minute half-life temperature: 136.1° C.), and1,1-di(tert-hexylperoxy) cyclohexane (one-minute half-life temperature:149.2° C.). In particular, di(4-tert-butylcyclohexyl) peroxydicarbonate(one-minute half-life temperature: 92.1° C.), dilauroyl peroxide(one-minute half-life temperature: 116.4° C.), dibenzoyl peroxide(one-minute half-life temperature: 130.0° C.), or the like is preferablyused, because they can provide high crosslinking reaction efficiency.

The half life of the peroxide is an indicator of how fast the peroxidecan be decomposed and refers to the time required for the amount of theperoxide to reach one half of its original value. The decompositiontemperature required for a certain half life and the half life timeobtained at a certain temperature are shown in catalogs furnished bymanufacturers, such as “Organic Peroxide Catalog, 9th Edition, May,2003” furnished by NOF CORPORATION.

The amount of the crosslinking agent (C) to be used is preferably from0.01 to 20 parts by weight, more preferably from 0.03 to 10 parts byweight, based on 100 parts by weight of the (meth)acrylic polymer (A).If the amount of the crosslinking agent (C) is less than 0.01 parts byweight, the cohesive strength of the pressure-sensitive adhesive maytend to be insufficient, and foaming may occur during heating. If theamount of the crosslinking agent (C) is more than 20 parts by weight,the humidity resistance may be insufficient, so that peeling may easilyoccur in a reliability test or the like.

One of the isocyanate crosslinking agents may be used alone, or amixture of two or more of the isocyanate crosslinking agents may beused. The total content of the polyisocyanate compound crosslinkingagent(s) is preferably from 0.01 to 2 parts by weight, more preferablyfrom 0.02 to 2 parts by weight, even more preferably from 0.05 to 1.5parts by weight, based on 100 parts by weight of the (meth)acrylicpolymer (A). The content may be appropriately controlled taking intoaccount the cohesive strength or the prevention of peeling in adurability test or the like.

One of the peroxide crosslinking agents may be used alone, or a mixtureof two or more of the peroxide crosslinking agent may be used. The totalcontent of the peroxide(s) is preferably from 0.01 to 2 parts by weight,more preferably from 0.04 to 1.5 parts by weight, even more preferablyfrom 0.05 to 1 part by weight, based on 100 parts by weight of the(meth)acrylic polymer (A). The content of the peroxide(s) may beappropriately selected in this range in order to control theworkability, reworkability, crosslink stability or peeling properties.

The amount of decomposition of the peroxide may be determined bymeasuring the peroxide residue after the reaction process by highperformance liquid chromatography (HPLC).

More specifically, for example, after the reaction process, about 0.2 gof each pressure-sensitive adhesive composition is taken out, immersedin 10 ml of ethyl acetate, subjected to shaking extraction at 25° C. and120 rpm for 3 hours in a shaker, and then allowed to stand at roomtemperature for 3 days. Thereafter, 10 ml of acetonitrile is added, andthe mixture is shaken at 25° C. and 120 rpm for 30 minutes. About 10 plof the liquid extract obtained by filtration through a membrane filter(0.45 μm) is subjected to HPLC by injection and analyzed so that theamount of the peroxide after the reaction process is determined.

The pressure-sensitive adhesive composition of the present invention mayfurther contain a silane coupling agent (D). The durability or thereworkability can be improved using the silane coupling agent (D).Examples of silane coupling agent include epoxy group-containing silanecoupling agents such as 3-glycidoxypropyltrimethoxysilane,3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane,and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containingsilane coupling agents such as 3-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine; (meth)acrylicgroup-containing silane coupling agents such as3-acryloxypropyltrimethoxysilane and3-methacryloxypropyltriethoxysilane; and isocyanate group-containingsilane coupling agents such as 3-isocyanatepropyltriethoxysilane.

One of the silane coupling agents (D) may be used alone, or a mixture oftwo or more of the silane coupling agents. The total content of thesilane coupling agent(s) is preferably from 0.001 to 5 parts by weight,more preferably from 0.01 to 1 part by weight, even more preferably from0.02 to 1 part by weight, still more preferably from 0.05 to 0.6 partsby weight, based on 100 parts by weight of the (meth)acrylic polymer(A). The content of the silane coupling agent may be appropriatelyamount in order to control improve durability and maintain adhesivestrength to the optical member such as a liquid crystal cell.

A polyether-modified silicone compound may be further added to thepressure-sensitive adhesive composition of the present invention. Forexample, the polyether-modified silicone compound disclosed in JP-A No.2010-275522 may be used.

The polyether-modified silicone compound has a polyether skeleton and areactive silyl group represented by formula (1): —SiR_(a)M_(3-a) at atleast one terminal, wherein R represents a monovalent organic grouphaving 1 to 20 carbon atoms and optionally having a substituent; Mrepresents a hydroxyl group or a hydrolyzable group, and <a> representsan integer of 0 to 2, provided that in cases where two or more R groups,R groups is the same or different, and in cases where two or more Mgroups, M groups is the same or different.

The polyether-modified silicone compound may be a compound representedby formula (2): R_(a)M_(3-a)Si—X—Y—(AO)_(n)—Z, wherein R represents amonovalent organic group having 1 to 20 carbon atoms and optionallyhaving a substituent, M represents a hydroxyl group or a hydrolyzablegroup; <a>represents an integer of 0 to 2, provided that in cases wheretwo or more R groups, R groups is the same or different, and in caseswhere two or more M groups, M groups is the same or different, AOrepresents a straight- or branched-chain oxyalkylene group of 1 to 10carbon atoms, n represents the average addition molar number of theoxyalkylene groups, which is from 1 to 1,700; X represents a straight-or branched-chain alkylene group of 1 to 20 carbon atoms, Y representsan ether bond, an ester bond, a urethane bond, or a carbonate bond and

Z represents a hydrogen atom, a monovalent hydrocarbon group of 1 to 10carbon atoms,

a group represented by formula (2A) : —Y¹—X—SiR_(a)M_(3-a), wherein R, Mand X have the same meanings as defined above; and Y¹ represents asingle bond, a —CO— bond, a —CONH— bond, or a —COO— bond, or

a group represented by formula (2B) :—Q(—(OA)_(n)—Y—X—SiR_(a)M_(3-a))_(m), wherein R, M, X, and Y have thesame meanings as defined above, OA has the same meaning as AO definedabove, n has the same meaning as defined above, Q represents a divalentor polyvalent hydrocarbon group of 1 to 10 carbon atoms, and mrepresents a number that is the same as the valence of the hydrocarbongroup.

Specific examples of the polyether-modified silicone compound include MSPolymers S203, S303 and S810 manufactured by Kaneka Corporation; SILYLEST250 and EST280 manufactured by Kaneka Corporation; SAT10, SAT200,SAT220, SAT350, and SAT400 manufactured by Kaneka Corporation; andEXCESTAR S2410, S2420 or S3430 manufacture by ASAHI GLASS CO., LTD.

The pressure-sensitive adhesive composition of the present invention mayalso contain any other known additive. For example, a polyether compoundsuch as a polyalkylen glycol exemplified a polypropylene glycol, apowder such as a colorant and a pigment, a tackifier, a dye, asurfactant, a plasticizer, a surface lubricant, a leveling agent, asoftening agent, an antioxidant, an age resister, a light stabilizer, anultraviolet absorbing agent, a polymerization inhibitor, an inorganic ororganic filler, a metal powder, or a particle- or foil-shaped materialmay be added as appropriate depending on the intended use. A redoxsystem including an added reducing agent may also be used in thecontrollable range.

The pressure-sensitive adhesive composition is used to form apressure-sensitive adhesive layer. To form the pressure-sensitiveadhesive layer, it is preferred that the total amount of the addition ofthe crosslinking agent should be controlled and that the effect of thecrosslinking temperature and the crosslinking time should be carefullytaken into account.

The crosslinking temperature and the crosslinking time may be controlleddepending on the crosslinking agent used. The crosslinking temperatureis preferably 170° C. or less.

The crosslinking process may be performed at the temperature of theprocess of drying the pressure-sensitive adhesive layer, or thecrosslinking process may be separately performed after the dryingprocess.

The crosslinking time is generally from about 0.2 to about 20 minutes,preferably from about 0.5 to about 10 minutes, while it may be settaking into account productivity and workability.

FIG. 1 is a cross-sectional view showing a pressure-sensitive adhesivelayer-attached polarizing film according to the invention. Asillustrated in FIG. 1, the pressure-sensitive adhesive layer-attachedpolarizing film of the present invention includes a polarizer, atransparent protective film provided on only one side of the polarizer,and a pressure-sensitive adhesive layer that is formed of thepressure-sensitive adhesive composition on the other side of thepolarizer, with no transparent protective layer provided on the otherside.

For example, the pressure-sensitive adhesive layer may be formed by amethod including applying the pressure-sensitive adhesive composition toa release-treated separator or the like, removing the polymerizationsolvent and so on by drying to form a pressure-sensitive adhesive layerand then transferring it to a polarizing film, or by a method includingapplying the pressure-sensitive adhesive composition to a polarizingfilm and removing the polymerization solvent and so on by drying to forma pressure-sensitive adhesive layer on the polarizing film. Before thepressure-sensitive adhesive is applied, in addition at least one solventother than the polymerization solvent may be added to thepressure-sensitive adhesive.

A silicone release liner is preferably used as the release-treatedseparator. The pressure-sensitive adhesive composition of the presentinvention may be applied to such a liner and dried to form apressure-sensitive adhesive layer. In this process, thepressure-sensitive adhesive may be dried using any appropriate methoddepending on the purpose. A method of drying by heating the coating filmis preferably used. The heat drying temperature is preferably from 40°C. to 200° C., more preferably from 50° C. to 180° C., particularlypreferably from 70° C. to 170° C. When the heating temperature is set inthe above range, a pressure-sensitive adhesive having good adhesiveproperties can be obtained.

Any appropriate drying time may be used. The drying time is preferablyfrom 5 seconds to 20 minutes, more preferably from 5 seconds to 10minutes, particularly preferably from 10 seconds to 5 minutes.

FIG. 2 is a cross-sectional view showing a pressure-sensitive adhesivelayer-attached polarizing film according to the invention. Asillustrated in FIG. 2, an anchor layer may also be formed on the surfaceof the polarizing film or the surface of the polarizing film may besubjected to any of various adhesion-facilitating treatments such as acorona treatment and a plasma treatment, and then forming thepressure-sensitive adhesive layer. The surface of the pressure-sensitiveadhesive layer may also be subjected to an adhesion-facilitatingtreatment.

Various methods may be used to foil the pressure-sensitive adhesivelayer. Specific examples of such methods include roll coating, kiss rollcoating, gravure coating, reverse coating, roll brush coating, spraycoating, dip roll coating, bar coating, knife coating, air knifecoating, curtain coating, lip coating, and extrusion coating with a diecoater or the like.

The thickness of the pressure-sensitive adhesive layer is typically, butnot limited to, from about 1 to 100 μm, preferably from 2 to 50 μm, morepreferably from 2 to 40 μm, further preferably from 5 to 35 μm.

When the pressure-sensitive adhesive layer is exposed, thepressure-sensitive adhesive layer may be protected with a sheet havingundergone release treatment (a separator) before practical use.

Examples of the material for forming the separator include a plasticfilm such as a polyethylene, polypropylene, polyethylene terephthalate,or polyester film, a porous material such as paper, cloth and nonwovenfabric, and an appropriate thin material such as a net, a foamed sheet,a metal foil, and a laminate thereof. In particular, a plastic film ispreferably used, because of its good surface smoothness.

The plastic film may be any film capable of protecting thepressure-sensitive adhesive layer, and examples thereof include apolyethylene film, a polypropylene film, a polybutene film, apolybutadiene film, a polymethylpentene film, a polyvinyl chloride film,a vinyl chloride copolymer film, a polyethylene terephthalate film, apolybutylene terephthalate film, a polyurethane film, and anethylene-vinyl acetate copolymer film.

The thickness of the separator is generally from about 5 to about 200μm, preferably from about 5 to about 100 μm. If necessary, the separatormay be treated with a release agent such as a silicone, fluorine,long-chain alkyl, or fatty acid amide release agent, or may be subjectedto release and antifouling treatment with silica powder or to antistatictreatment of coating type, kneading and mixing type, vapor-depositiontype, or the like. In particular, if the surface of the separator isappropriately subjected to release treatment such as silicone treatment,long-chain alkyl treatment, and fluorine treatment, the releasabilityfrom the pressure-sensitive adhesive layer can be further increased.

In the above production method, the release-treated sheet may be usedwithout modification as a separator for the pressure-sensitive adhesivesheet, the pressure-sensitive adhesive layer-attached polarizing film orthe like, so that the process can be simplified.

The polarizing film to be used has a polarizer and a transparentprotective film provided on only one side of the polarizer.

A polarizer is not limited especially but various kinds of polarizer maybe used. As a polarizer, for example, a film that is uniaxiallystretched after having dichromatic substances, such as iodine anddichromatic dye, absorbed to hydrophilic high molecular weight polymerfilms, such as polyvinyl alcohol-based film, partially formalizedpolyvinyl alcohol-based film, and ethylene-vinyl acetate copolymer-basedpartially saponified film; poly-ene-based alignment films, such asdehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride,etc. may be mentioned. In these, a polyvinyl alcohol-based film on whichdichromatic materials such as iodine, is absorbed and aligned afterstretched is suitably used. Although thickness of polarizer is notespecially limited, the thickness of about 80 μm or less is commonlyadopted.

A polarizer that is uniaxially stretched after a polyvinyl alcohol-basedfilm dyed with iodine is obtained by stretching a polyvinylalcohol-based film by 3 to 7 times the original length, after dipped anddyed in aqueous solution of iodine. If needed the film may also bedipped in aqueous solutions, such as boric acid and potassium iodide,which may include zinc sulfate, zinc chloride. Furthermore, beforedyeing, the polyvinyl alcohol-based film may be dipped in water andrinsed if needed. By rinsing polyvinyl alcohol-based film with water,effect of preventing un-uniformity, such as unevenness of dyeing, isexpected by making polyvinyl alcohol-based film swelled in addition thatalso soils and blocking inhibitors on the polyvinyl alcohol-based filmsurface may be washed off. Stretching may be applied after dyed withiodine or may be applied concurrently, or conversely dyeing with iodinemay be applied after stretching. Stretching is applicable in aqueoussolutions, such as boric acid and potassium iodide, and in water bath.

A thin polarizer with a thickness of 10 μm or less may also be used. Inview of thinning, the thickness is preferably from 1 to 7 μm. Such athin polarizer is less uneven in thickness, has good visibility, and isless dimensionally-variable and therefore has high durability. It isalso preferred because it can form a thinner polarizing film.

Typical examples of such a thin polarizer include the thin polarizinglayers disclosed in JP-A No. 51-069644, JP-A No. 2000-338329,WO2010/100917, specification of PCT/JP2010/001460, specification ofJapanese Patent Application No. 2010-269002, or specification ofJapanese Patent Application No. 2010-263692. These thin polarizinglayers can be obtained by a process including the steps of stretching alaminate of a polyvinyl alcohol-based resin (hereinafter also referredto as PVA-based resin) layer and a stretchable resin substrate anddyeing the laminate. Using this process, the PVA-based resin layer, evenwhen thin, can be stretched without problems such as breakage, whichwould otherwise be caused by stretching of the layer supported on astretchable resin substrate.

Among processes including the steps of stretching and dyeing a laminate,a process capable of high-ratio stretching to improve polarizingperformance is preferably used to obtain the thin polarizing layer.Therefore, the thin polarizing layer is preferably obtained by a processincluding the step of stretching in an aqueous boric acid solution asdisclosed in WO2010/100917, the specification of PCT/JP2010/001460, thespecification of Japanese Patent Application No. 2010-269002, or thespecification of Japanese Patent Application No. 2010-263692, inparticular, preferably obtained by a process including the step ofperforming auxiliary in-air stretching before stretching in an aqueousboric acid solution as disclosed in the specification of Japanese PatentApplication No. 2010-269002 or the specification of Japanese PatentApplication or 2010-263692.

The specification of PCT/JP2010/001460 discloses a thinhighly-functional polarizing layer that is formed integrally with aresin substrate, made of a PVA-based resin containing an orienteddichroic material, and has a thickness of 7 μm or less and the opticalproperties of a single transmittance of 42.0% or more and a degree ofpolarization of 99.95% or more.

This thin highly-functional polarizing layer can be produced by aprocess including forming a PVA-based resin coating on a resin substratewith a thickness of at least 20 μm, drying the coating to form aPVA-based resin layer, immersing the resulting PVA-based resin layer ina dyeing liquid containing a dichroic material to absorb the dichroicmaterial to the PVA-based resin layer, and stretching the PVA-basedresin layer, which contains the absorbed dichroic material, togetherwith the resin substrate in an aqueous boric acid solution to a totalstretch ratio of 5 times or more the original length.

A laminated film having a thin highly-functional polarizing layercontaining an oriented dichroic material can be produced by a methodincluding the steps of: coating a PVA-based resin-containing aqueoussolution to one side of a resin substrate with a thickness of at least20 μm, drying the coating to form a PVA-based resin layer so that alaminated film including the resin substrate and the PVA-based resinlayer formed thereon is produced; immersing the laminated film in adyeing liquid containing a dichroic material to absorb the dichroicmaterial to the PVA-based resin layer in the laminated film, wherein thelaminated film includes the resin substrate and the PVA-based resinlayer formed on one side of the resin substrate; and stretching thelaminated film, which has the PVA-based resin layer containing theabsorbed dichroic material, in an aqueous boric acid solution to a totalstretch ratio of 5 times or more the original length, wherein thePVA-based resin layer containing the absorbed dichroic material isstretched together with the resin substrate, so that a laminated filmincluding the resin substrate and a thin highly-functional polarizinglayer formed on one side of the resin substrate is produced, in whichthe thin highly-functional polarizing layer is made of the PVA-basedresin layer containing the oriented dichroic material and has athickness of 7 μm or less and the optical properties of a singletransmittance of 42.0% or more and a degree of polarization of 99.95% ormore.

In the pressure-sensitive adhesive layer-attached polarizing filmaccording to an embodiment of the present invention, the polarizer witha thickness of 10 μm or less may be a polarizing layer of a continuousweb including a PVA-based resin containing an oriented dichroicmaterial, which is obtained by a two-stage stretching process includingauxiliary in-air stretching of a laminate and stretching of the laminatein an aqueous boric acid solution, wherein the laminate includes athermoplastic resin substrate and a polyvinyl alcohol-based resin layerformed thereon. The thermoplastic resin substrate is preferably anamorphous ester-based thermoplastic resin substrate or a crystallineester-based thermoplastic resin substrate.

The thin polarizing layer disclosed in the specification of JapanesePatent Application No. 2010-269002 or the specification of JapanesePatent Application No. 2010-263692 is a polarizing layer in the form ofa continuous web including a PVA-based resin containing an orienteddichroic material, which is made with a thickness of 10 μm or less by atwo-stage stretching process including auxiliary in-air stretching of alaminate and stretching of the laminate in an aqueous boric acidsolution, wherein the laminate includes an amorphous ester-basedthermoplastic resin substrate and a PVA-based resin layer formedthereon. This thin polarizing layer is preferably made to have opticalproperties satisfying the following requirements:P>−(10^(0.929T-42.4)−1)×100 (provided that T<42.3) and P≥99.9 (providedthat T≥42.3), wherein T represents the single transmittance, and Prepresents the degree of polarization.

Specifically, the thin polarizing layer can be produced by a thinpolarizing layer-manufacturing method including the steps of: performingelevated temperature in-air stretching of a PVA-based resin layer, sothat a stretched intermediate product including an oriented PVA-basedresin layer is produced, wherein the PVA-based resin layer is formed onan amorphous ester-based thermoplastic resin substrate in the form of acontinuous web; absorbing a dichroic material (which is preferablyiodine or a mixture of iodine and an organic dye) to the stretchedintermediate product to produce a colored intermediate product includingthe PVA-based resin layer in which the dichroic material is oriented;and performing stretching of the colored intermediate product in anaqueous boric acid solution so that a polarizing layer with a thicknessof 10 μm or less is produced, which includes the PVA-based resin layercontaining the oriented dichroic material.

In this manufacturing method, the elevated temperature in-air stretchingand the stretching in an aqueous boric acid solution are preferablyperformed in such a manner that the PVA-based resin layer formed on theamorphous ester-based thermoplastic resin substrate is stretched to atotal stretch ratio of 5 times or more. The aqueous boric acid solutionpreferably has a temperature of 60° C. or more for the stretchingtherein. Before stretched in the aqueous boric acid solution, thecolored intermediate product is preferably subjected to aninsolubilization treatment, in which the colored intermediate product ispreferably immersed in an aqueous boric acid solution with a temperatureof 40° C. or less. The amorphous ester-based thermoplastic resinsubstrate may be made of amorphous polyethylene terephthalate includingco-polyethylene terephthalate in which isophthalic acid,cyclohexanedimethanol, or any other monomer is copolymerized, and ispreferably made of a transparent resin. The thickness of the substratemay be at least seven times the thickness of the PVA-based resin layerto be formed. The elevated temperature in-air stretching is preferablyperformed at a stretch ratio of 3.5 times or less, and the temperatureof the elevated temperature in-air stretching is preferably equal to orhigher than the glass transition temperature of the PVA-based resin.Specifically, it is preferably in the range of 95° C. to 150° C. Whenthe elevated temperature in-air stretching is end-free uniaxialstretching, the PVA-based resin layer formed on the amorphousester-based thermoplastic resin substrate is preferably stretched to atotal stretch ratio of from 5 to 7.5 times. When the elevatedtemperature in-air stretching is fixed-end uniaxial stretching, thePVA-based resin layer formed on the amorphous ester-based thermoplasticresin substrate is preferably stretched to a total stretch ratio of from5 to 8.5 times.

More specifically, the thin polarizing layer can be produced by themethod described below.

A substrate in the form of a continuous web is prepared, which is madeof co-polymerized polyethylene terephthalate (amorphous PET) in which 6mol % of isophthalic acid is copolymerized. The amorphous PET has aglass transition temperature of 75° C. A laminate of a polyvinyl alcohol(PVA) layer and the amorphous PET substrate in the form of a continuousweb is prepared as described below. Incidentally, the glass transitiontemperature of PVA is 80° C.

A 200 μm thick amorphous PET substrate is provided, and an aqueous 4-5%PVA solution is prepared by dissolving PVA powder with a polymerizationdegree of 1,000 or more and a saponification degree of 99% or more inwater. Subsequently, the aqueous PVA solution is applied to a 200 μmthick amorphous PET substrate and dried at a temperature of 50 to 60° C.so that a laminate composed of the amorphous PET substrate and a 7 μmthick PVA layer formed thereon is obtained.

The laminate having the 7 μm thick PVA layer is subjected to a two-stagestretching process including auxiliary in-air stretching and stretchingin an aqueous boric acid solution as described below, so that a thinhighly-functional polarizing layer with a thickness of 3 μm is obtained.At the first stage, the laminate having the 7 μm thick PVA layer issubjected to an auxiliary in-air stretching step so that the layer isstretched together with the amorphous PET substrate to form a stretchedlaminate having a 5 μm thick PVA layer. Specifically, the stretchedlaminate is formed by a process including feeding the laminate havingthe 7 μm thick PVA layer to a stretching apparatus placed in an ovenwith the stretching temperature environment set at 130° C. andsubjecting the laminate to end-free uniaxial stretching to a stretchratio of 1.8 times. In the stretched laminate, the PVA layer ismodified, by the stretching, into a 5 μm thick PVA layer containingoriented PVA molecules.

Subsequently, a dyeing step is performed to produce a colored laminatehaving a 5 μm thick PVA layer containing oriented PVA molecules andabsorbed iodine. Specifically, the colored laminate is produced byimmersing the stretched laminate for a certain time period in a dyeingliquid containing iodine and potassium iodide and having a temperatureof 30° C. so that iodine can be absorbed to the PVA layer of thestretched laminate and that the PVA layer for finally forming ahighly-functional polarizing layer can have a single transmittance of 40to 44%. In this step, the dyeing liquid contains water as a solvent andhas an iodine concentration in the range of 0.12 to 0.30% by weight anda potassium iodide concentration in the range of 0.7 to 2.1% by weight.The concentration ratio of iodine to potassium iodide is 1:7. It shouldbe noted that potassium iodide is necessary to make iodine soluble inwater. More specifically, the stretched laminate is immersed for 60seconds in a dyeing liquid containing 0.30% by weight of iodine and 2.1%by weight of potassium iodide, so that a colored laminate is produced,in which the 5 μm thick PVA layer contains oriented PVA molecules andabsorbed iodine.

At the second stage, the colored laminate is further subjected to astretching step in an aqueous boric acid so that the layer is furtherstretched together with the amorphous PET substrate to form an opticalfilm laminate having a 3 μm thick PVA layer, which forms ahighly-functional polarizing layer. Specifically, the optical filmlaminate is formed by a process including feeding the colored laminateto a stretching apparatus placed in a treatment system in which anaqueous boric acid solution containing boric acid and potassium iodideis set in the temperature range of 60 to 85° C. and subjecting thelaminate to end-free uniaxial stretching to a stretch ratio of 3.3times. More specifically, the aqueous boric acid solution has atemperature of 65° C. In the solution, the boric acid content and thepotassium iodide content are 4 parts by weight and 5 parts by weight,respectively, based on 100 parts by weight of water. In this step, thecolored laminate having a controlled amount of absorbed iodine is firstimmersed in the aqueous boric acid solution for 5 to 10 seconds.Subsequently, the colored laminate is directly fed between a pluralityof pairs of rolls different in peripheral speed, which form thestretching apparatus placed in the treatment system, and subjected toend-free uniaxial stretching for 30 to 90 seconds to a stretch ratio of3.3 times. This stretching treatment converts the PVA layer of thecolored laminate to a 3 μm thick PVA layer in which the absorbed iodineforms a polyiodide ion complex highly oriented in a single direction.This PVA layer forms a highly-functional polarizing layer in the opticalfilm laminate.

A washing step, which is however not essential for the manufacture ofthe optical film laminate, is preferably performed, in which the opticalfilm laminate is taken out of the aqueous boric acid solution, and boricacid deposited on the surface of the 3 μm thick PVA layer formed on theamorphous PET substrate is washed off with an aqueous potassium iodidesolution. Subsequently, the washed optical film laminate is dried in adrying step using warm air at 60° C. It should be noted that the washingstep is to prevent appearance defects such as boric acid precipitation.

A lamination and/or transfer step, which is also not essential for themanufacture of the optical film laminate, may also be performed, inwhich an 80 μm thick triacetylcellulose film is laminated to the surfaceof the 3 μm thick PVA layer formed on the amorphous PET substrate, whilean adhesive is applied to the surface, and then the amorphous PETsubstrate is peeled off, so that the 3 μm thick PVA layer is transferredto the 80 μm thick triacetylcellulose film.

[Other Steps]

The thin polarizing layer-manufacturing method may include additionalsteps other than the above steps. For example, additional steps mayinclude an insolubilization step, a crosslinking step, a drying step(moisture control), etc. Additional steps may be performed at anyappropriate timing.

The insolubilization step is typically achieved by immersing thePVA-based resin layer in an aqueous boric acid solution. Theinsolubilization treatment can impart water resistance to the PVA-basedresin layer. The concentration of boric acid in the aqueous boric acidsolution is preferably from 1 to 4 parts by weight based on 100 parts byweight of water. The insolubilization bath (aqueous boric acid solution)preferably has a temperature of 20° C. to 50° C. Preferably, theinsolubilization step is performed after the preparation of the laminateand before the dyeing step or the step of stretching in water.

The crosslinking step is typically achieved by immersing the PVA-basedresin layer in an aqueous boric acid solution. The crosslinkingtreatment can impart water resistance to the PVA-based resin layer. Theconcentration of boric acid in the aqueous boric acid solution ispreferably from 1 to 4 parts by weight based on 100 parts by weight ofwater. When the crosslinking step is performed after the dyeing step, aniodide is preferably added to the solution. The addition of an iodidecan suppress the elution of absorbed iodine from the PVA-based resinlayer. The amount of the addition of an iodide is preferably from 1 to 5parts by weight based on 100 parts by weight of water. Examples of theiodide include those listed above. The temperature of the crosslinkingbath (aqueous boric acid solution) is preferably from 20° C. to 50° C.Preferably, the crosslinking step is performed before the secondstretching step in the aqueous boric acid solution. In a preferredembodiment, the dyeing step, the crosslinking step, and the secondstretching step in the aqueous boric acid solution are performed in thisorder.

A thermoplastic resin with a high level of transparency, mechanicalstrength, thermal stability, moisture blocking properties, isotropy, andthe like may be used as a material for forming the transparentprotective film. Examples of such a thermoplastic resin includecellulose resins such as triacetylcellulose, polyester resins,polyethersulfone resins, polysulfone resins, polycarbonate resins,polyamide resins, polyimide resins, polyolefin resins, (meth)acrylicresins, cyclic olefin polymer resins (norbornene resins), polyarylateresins, polystyrene resins, polyvinyl alcohol resins, and any mixturethereof. The transparent protective film is generally laminated to oneside of the polarizer with the adhesive layer, but thermosetting resinsor ultraviolet curing resins such as (meth)acrylic, urethane, acrylicurethane, epoxy, or silicone resins may be used to other side of thepolarizer for the transparent protective film. The transparentprotective film may also contain at least one type of any appropriateadditive. Examples of the additive include an ultraviolet absorbingagent, an antioxidant, a lubricant, a plasticizer, a release agent, ananti-discoloration agent, a flame retardant, a nucleating agent, anantistatic agent, a pigment, and a colorant. The content of thethermoplastic resin in the transparent protective film is preferablyfrom 50 to 100% by weight, more preferably from 50 to 99% by weight,still more preferably from 60 to 98% by weight, particularly preferablyfrom 70 to 97% by weight. If the content of the thermoplastic resin inthe transparent protective film is 50% by weight or less, hightransparency and other properties inherent in the thermoplastic resincan fail to be sufficiently exhibited.

The transparent protective film is bonded to one side of the polarizerwith an adhesive layer interposed therebetween. The polarizer and thetransparent protective film are bonded together using an adhesive. Forexample, the adhesive may be an isocyanate-based adhesive, a polyvinylalcohol-based adhesive, a gelatin-based adhesive, a vinyl latex-basedadhesive, an aquatic polyester-based adhesive, or the like. The adhesiveis generally used in the form of an aqueous solution, which generallyhas a solids content of 0.5 to 60% by weight. Besides the above, theadhesive between the polarizer and the transparent protective film mayalso be an ultraviolet-curable adhesive, an electron beam-curableadhesive, or the like. Electron beam-curable adhesives for polarizingfilms have good tackiness to the above various transparent protectivefilms. The adhesive for use in the present invention may also contain ametal compound filler.

The polarizing film may be laminate to other optical film. Other opticalfilm may be used as other optical layers, such as a reflective plate, atransflective plate, a retardation film (a half wavelength plate and aquarter wavelength plate included), and a viewing angle compensationfilm, which may be used for formation of a liquid crystal display etc..These are used in practice as an optical film, or as one layer or twolayers or more of optical layers laminated with polarizing film.

Although an optical film with the above described optical layerlaminated to the polarizing film may be formed by a method in whichlaminating is separately carried out sequentially in manufacturingprocess of a liquid crystal display etc., an optical film in a form ofbeing laminated beforehand has an outstanding advantage that it hasexcellent stability in quality and assembly workability, etc., and thusmanufacturing processes ability of a liquid crystal display etc. may beraised. Proper adhesion means, such as a pressure-sensitive adhesivelayer, may be used for laminating. On the occasion of adhesion of theabove described polarizing film and other optical layers, the opticalaxis may be set as a suitable configuration angle according to thetarget retardation characteristics etc.

FIG. 3 is a cross-sectional view showing a liquid crystal displayaccording to the invention. As illustrated in FIG. 3, thepressure-sensitive adhesive layer-attached polarizing film of thepresent invention is preferably used to form various types of imagedisplays such as liquid crystal displays. Liquid crystal displays may beformed according to conventional techniques. Specifically, liquidcrystal displays are generally formed by appropriately assembling aliquid crystal cell and the pressure-sensitive adhesive layer-attachedpolarizing film and optionally other component such as a lighting systemand incorporating a driving circuit according to any conventionaltechnique, except that the pressure-sensitive adhesive layer-attachedpolarizing film of the present invention is used. Any type of liquidcrystal cell may also be used such as a TN type, an STN type, a n type aVA type and IPS type.

Suitable liquid crystal displays, such as liquid crystal display withwhich the pressure-sensitive adhesive layer-attached polarizing film hasbeen located at one side or both sides of the liquid crystal cell, andwith which a backlight or a reflective plate is used for a lightingsystem may be manufactured. In this case, the optical film may beinstalled in one side or both sides of the liquid crystal cell. Wheninstalling the optical films in both sides, they may be of the same typeor of different type. Furthermore, in assembling a liquid crystaldisplay, suitable parts, such as diffusion layer, anti-glare layer,antireflection film, protective plate, prism array, lens array sheet,optical diffusion sheet, and backlight, may be installed in suitableposition in one layer or two or more layers.

EXAMPLES

The present invention is more specifically described by the examplesbelow, which are not intended to limit the scope of the presentinvention. In each example, parts and % are all by weight. Unlessotherwise stated below, the conditions of room temperature standing are23° C. and 65% RH in all the cases.

<Measurement of Weight Average Molecular Weight of (Meth)acrylic Polymer(A)>

The weight average molecular weight (Mw) of the (meth)acrylic polymer(A) was measured by GPC (Gel Permeation Chromatography).

-   Analyzer: HLC-8120GPC manufactured by TOSOH CORPORATION-   Columns: G7000H_(XL)+GMH_(XL)+GMH_(XL) manufactured by TOSOH    CORPORATION-   Column size: each 7.8 mmφ×30 cm, 90 cm in total-   Colum temperature: 40° C.-   Flow rate: 0.8 ml/minute-   Injection volume: 100 μl-   Eluent: tetrahydrofuran-   Detector: differential refractometer (RI)-   Standard sample: polystyrene

<Preparation of Polarizing Film (1)>

A process for forming a thin polarizing layer was performed. In theprocess, a laminate including an amorphous PET substrate and a 9 μmthick PVA layer formed thereon was first subjected to auxiliary in-airstretching at a stretching temperature of 130° C. to form a stretchedlaminate. Subsequently, the stretched laminate was subjected to dyeingto form a colored laminate, and the colored laminate was subjected tostretching in an aqueous boric acid solution at a stretching temperatureof 65° C. to a total stretch ratio of 5.94 times, so that an opticalfilm laminate was obtained, which had a 4 μm thick PVA layer stretchedtogether with the amorphous PET substrate. Such two-stage stretchingsuccessfully formed an optical film laminate having a 4 μm thick PVAlayer, which was formed on the amorphous PET substrate, contained highlyoriented PVA molecules, and formed a highly-functional polarizing layerin which iodine absorbed by the dyeing formed a polyiodide ion complexoriented highly in a single direction. An 40 μm thick saponifiedtriacetylcellulose film was further attached to the surface of thepolarizing layer of the optical film laminate, while a polyvinylalcohol-based adhesive was applied to the surface, and then theamorphous PET substrate was peeled off, so that a polarizing film with athin polarizing layer was obtained. Hereinafter, this is referred to asthin polarizing film (1).

(Preparation of Polarizing film (2))

An 80 μm-thick polyvinyl alcohol film was stretched to 3 times betweenrolls different in velocity ratio, while it was dyed in a 0.3% iodinesolution at 30° C. for 1 minute. The film was then stretched to a totalstretch ratio of 6 times, while it was immersed in an aqueous solutioncontaining 4% of boric acid and 10% of potassium iodide at 60° C. for0.5 minutes. The film was then washed by immersion in an aqueoussolution containing 1.5% of potassium iodide at 30° C. for 10 secondsand then dried at 50° C. for 4 minutes to give a polarizer with athickness of 20 μm. Saponified triacetylcellulose films each with athickness of 40 pm were bonded to both sides of the polarizer with apolyvinyl alcohol adhesive to form a polarizing film. Hereinafter, thisis referred to as TAC polarizing film (2).

Production Example 1 <Preparation of Acryl-Based Polymer (A-1)>

To a four-neck flask equipped with a stirring blade, a thermometer, anitrogen gas introducing tube, and a condenser were added a monomermixture containing 82 parts of butyl acrylate, 15 parts of benzylacrylate, and 3 parts of 4-hydroxybutyl acrylate. Based on 100 parts(solid basis) of the monomer mixture, 0.1 parts of2,2′-azobisisobutyronitrile as a polymerization initiator was furtheradded together with ethyl acetate. Nitrogen gas was introduced toreplace the air, while the mixture was gently stirred, and then apolymerization reaction was performed for 7 hours, while the temperatureof the liquid in the flask was kept at about 60° C. Subsequently, ethylacetate was added to the resulting reaction liquid to adjust the solidscontent to 30%, so that a solution of an acryl-based polymer (A-1) witha weight average molecular weight of 1,000,000 was obtained.

Production Example 2 <Preparation of Acryl-Based Polymer (A-2)>

A solution of an acryl-based polymer (A-2) with a weight averagemolecular weight of 1,000,000 was prepared as in Production Example 1,except that a monomer mixture containing 76.8 parts of butyl acrylate,10 parts of benzyl acrylate, 10 parts of phenoxyethyl acrylate, 3 partsof 4-hydroxybutyl acrylate, and 0.2 parts of acrylic acid was usedinstead.

Production Example 3 <Preparation of Acryl-Based Polymer (A-3)>

A solution of an acryl-based polymer (A-3) with a weight averagemolecular weight of 1,000,000 was prepared as in Production Example 1,except that a monomer mixture containing 81.9 parts of butyl acrylate,13 parts of benzyl acrylate, 0.1 parts of 2-hydroxyethyl acrylate, and 5parts of acrylic acid was used instead.

Example 1 (Preparation of Pressure-Sensitive Adhesive Composition)

Based on 100 parts of the solids of the acryl-based polymer (A-1)solution obtained in Production Example 1, 0.002 parts of lithiumbis(trifluoromethanesulfonyl)imide (manufactured by Japan Carlit Co.,Ltd.), 0.1 parts of trimethylolpropane xylylene diisocyanate (TakenateD110N, manufactured by Mitsui Chemicals, Inc.), 0.3 parts of dibenzoylperoxide, and 0.075 parts of γ-glycidoxypropyltrimethoxysilane (KBM-403,manufactured by Shin-Etsu Chemical Co., Ltd.) were added to theacryl-based polymer (A-1) solution, so that an acryl-basedpressure-sensitive adhesive solution was obtained.

(Preparation of Pressure-Sensitive Adhesive Layer-Attached PolarizingFilm)

Subsequently, the acryl-based pressure-sensitive adhesive solution wasuniformly applied to the surface of a silicone release agent-treatedpolyethylene terephthalate film (separator film) with a fountain coater,and dried for 2 minutes in an air circulation-type thermostatic oven at155° C., so that a 20 μm thick pressure-sensitive adhesive layer wasformed on the surface of the separator film. Subsequently, thepressure-sensitive adhesive layer was transferred from the separatorfilm to the polarizing layer side of the thin polarizing film (1)prepared as described above, so that a pressure-sensitive adhesivelayer-attached polarizing film was obtained.

Examples 2 to 17 and Comparative Examples 1 to 4

Pressure-sensitive adhesive layer-attached polarizing films wereprepared as in Example 1, except that in the preparation of thepressure-sensitive adhesive composition, the amount of each componentwas changed as shown in Table 1 and that in the preparation of thepressure-sensitive adhesive layer-attached polarizing film, the type ofthe polarizing film was changed as shown in Table 1.

The pressure-sensitive adhesive layer-attached polarizing film obtainedin each of the examples and the comparative examples was evaluated asdescribed below. The results of the evaluation are shown in Table 1.

<Surface Resistance (Initial)>

After the separator film was peeled off from the pressure-sensitiveadhesive layer-attached polarizing film, the surface resistance(Ω/square) of the surface of the pressure-sensitive adhesive wasmeasured using MCP-HT450 manufactured by Mitsubishi Chemical AnalytechCo., Ltd.

<Evaluation of Static Electricity-Induced Unevenness>

The prepared pressure-sensitive adhesive layer-attached polarizing filmwas cut into a piece with a size of 100 mm×100 mm, which was bonded to aliquid crystal panel. The panel was placed on a backlight with abrightness of 10,000 cd, and the orientation of the liquid crystal wasdisturbed using 5 kV static electricity produced by an electrostaticgenerator, ESD, (ESD-8012A, manufactured by Sanki Electronic IndustriesCo., Ltd.). The time required for recovery from the orientationfailure-induced display failure was measured using an instantaneousmultichannel photodetector system (MCPD-3000, manufactured by OtsukaElectronics Co., Ltd.), and evaluated according to the criteria below.

-   ⊙: Display failure was eliminated in a time of less than one second.-   ◯: Display failure was eliminated in a time of one second to less    than 10 seconds.-   ×: Display failure was eliminated in a time of 10 seconds or more.

<Durability>

The separator film was peeled off from the pressure-sensitive adhesivelayer-attached polarizing film, and the polarizing film was bonded to a0.7 mm thick non-alkali glass plate (1737, manufactured by CorningIncorporated) using a laminator. Subsequently, the laminate wasautoclaved at 50° C. and 0.5 MPa for 15 minutes, so that thepressure-sensitive adhesive layer-attached polarizing film wascompletely bonded to the non-alkali glass plate. Subsequently, thelaminate was stored in a heating oven at 80° C. (heating) and stored ina thermo-hygrostat under the conditions of 60° C./90% RH(humidification), respectively, and after 500 hours, the presence orabsence of peeling of the polarizing film was evaluated according to thecriteria below.

-   ⊙: No peeling was detected at all.-   ◯: Peeling was detected at an invisible level.-   Δ: Visible small peeling was detected.-   ×: Significant peeling was detected.

<Measurement of Polarization>

The separator film was peeled off from the pressure-sensitive adhesivelayer-attached polarizing film, and the polarizing film was bonded to a0.7 mm thick non-alkali glass plate (1737, manufactured by CorningIncorporated) using a laminator. Subsequently, the laminate wasautoclaved at 50° C. and 0.5 MPa for 15 minutes, so that thepressure-sensitive adhesive layer-attached polarizing film wascompletely bonded to the non-alkali glass plate. Subsequently, thelaminate was stored in a thermo-hygrostat at 60° C./95% RH for 500hours. The degree of polarization of the polarizing film was measuredusing V7100 manufactured by JASCO Corporation before and after thestorage, and the amount of change ΔP=(the degree of polarization beforethe storage)−(the degree of polarization after the storage) wascalculated.

TABLE 1 Pressure-sensitive adhesive composition Crosslinking agentPolarizing film (Meth)acryl- Alkali (C) Silane Additional Polarizerbased metal salt Isocyanate coupling compound thickness polymer (A) (B)type Peroxide agent (D) (E) Type (μm) Type Parts Type Parts Type PartsType Parts Type Parts Type Parts Example 1 Thin 4 A-1 100 B-1 0.002 C-10.1 C-3 0.3 D-1 0.075 polarizing film (1) Example 2 Thin 4 A-1 100 B-10.02 C-1 0.1 C-3 0.3 D-1 0.075 polarizing film (1) Example 3 Thin 4 A-1100 B-1 0.2 C-1 0.1 C-3 0.3 D-1 0.075 polarizing film (1) Example 4 Thin4 A-1 100 B-1 1 C-1 0.1 C-3 0.3 D-1 0.075 polarizing film (1) Example 5Thin 4 A-1 100 B-1 4 C-1 0.1 C-3 0.3 D-1 0.075 polarizing film (1)Example 6 TAC 20 A-1 100 B-1 0.002 C-1 0.1 C-3 0.3 D-1 0.075 polarizingfilm (2) Example 7 TAC 20 A-1 100 B-1 0.02 C-1 0.1 C-3 0.3 D-1 0.075polarizing film (2) Example 8 TAC 20 A-1 100 B-1 0.2 C-1 0.1 C-3 0.3 D-10.075 polarizing film (2) Example 9 TAC 20 A-1 100 B-1 1 C-1 0.1 C-3 0.3D-1 0.075 polarizing film (2) Example 10 TAC 20 A-1 100 B-1 4 C-1 0.1C-3 0.3 D-1 0.075 polarizing film (2) Example 11 Thin 4 A-1 100 B-1 0.2C-1 0.1 C-3 0.3 D-1 0.075 E-1 0.5 polarizing film (1) Example 12 Thin 4A-1 100 B-1 0.2 C-1 0.1 C-3 0.3 D-1 0.075 E-2 0.5 polarizing film (1)Example 13 Thin 4 A-1 100 B-2 0.2 C-1 0.1 C-3 0.3 D-1 0.075 polarizingfilm (1) Example 14 Thin 4 A-2 100 B-1 0.2 C-1 0.1 C-3 0.3 D-1 0.075polarizing film (1) Example 15 Thin 4 A-2 100 B-2 0.2 C-1 0.1 C-3 0.3D-1 0.075 polarizing film (1) Example 16 Thin 4 A-3 100 B-1 0.2 C-2 0.6— — D-1 0.075 polarizing film (1) Example 17 Thin 4 A-3 100 B-2 0.2 C-20.6 — — D-1 0.075 polarizing film (1) Comparative Thin 4 A-1 100 B-30.02 C-1 0.1 C-3 0.3 D-1 0.075 Example 1 polarizing film (1) ComparativeThin 4 A-1 100 B-3 0.2 C-1 0.1 C-3 0.3 D-1 0.075 Example 2 polarizingfilm (1) Comparative TAC 20 A-1 100 B-3 0.02 C-1 0.1 C-3 0.3 D-1 0.075Example 3 polarizing film (2) Comparative TAC 20 A-1 100 B-3 0.2 C-1 0.1C-3 0.3 D-1 0.075 Example 4 polarizing film (2) Evaluation StaticPolarization Surface electricity- degree resistance induced Durabilityreduction (Ω/square) unevenness Heating Humidification

Example 1 1.3E+12 ◯ ⊙ ⊙ 0.01 Example 2 8.8E+11 ⊙ ⊙ ⊙ 0.01 Example 34.5E+11 ⊙ ⊙ ⊙ 0.02 Example 4 8.8E+09 ⊙ ⊙ ⊙ 0.02 Example 5 1.4E+09 ⊙ ⊙ ◯0.02 Example 6 1.5E+12 ◯ ⊙ ⊙ 0.01 Example 7 9.0E+11 ⊙ ⊙ ⊙ 0.01 Example 84.2E+11 ⊙ ⊙ ⊙ 0.02 Example 9 8.1E+09 ⊙ ⊙ ⊙ 0.01 Example 10 1.2E+09 ⊙ ⊙ ◯0.02 Example 11 3.6E+11 ⊙ ⊙ ⊙ 0.01 Example 12 5.0E+11 ⊙ ⊙ ⊙ 0.02 Example13 2.6E+11 ⊙ ⊙ ⊙ 0.01 Example 14 6.3E+11 ⊙ ⊙ ⊙ 0.02 Example 15 5.3E+10 ⊙⊙ ⊙ 0.03 Example 16 7.3E+10 ⊙ ⊙ ⊙ 0.05 Example 17 6.1E+11 ⊙ ⊙ ⊙ 0.05Comparative 3.9E+12 ⊙ ⊙ ⊙ 1.1 Example 1 Comparative 1.2E+12 ⊙ ⊙ ⊙ 2.6Example 2 Comparative 3.8E+12 ⊙ X X 0.8 Example 3 Comparative 1.4E+12 ⊙X X 1.2 Example 4

In the alkali metal salt (B) column of Table 1, “B-1” represents lithiumbis(trifluoromethanesulfonyl)imide manufactured by Japan Carlit Co.,Ltd., “B-2” lithium perchloride manufactured by Japan Carlit Co., Ltd.,and “B-3” 1-hexyl-4-methylpyridinium hexafluorophosphate manufactured byKANTO CHEMICAL CO., INC.

In the crosslinking agent (C) column, “C-1” represents an isocyanatecrosslinking agent manufactured by Mitsui Takeda Chemicals, Inc.(Takenate D110N, trimethylolpropane xylylene diisocyanate), “C-2” anisocyanate crosslinking agent manufactured by Nippon PolyurethaneIndustry Co., Ltd. (CORONATE L, tolylene diisocyanate adduct oftrimethylolpropane), and “C-3” benzoyl peroxide manufactured by NOFCORPORATION (NYPER BMT).

In the silane coupling agent (D) column, “D-1” represents KBM403manufactured by Shin-Etsu Chemical Co., Ltd.

In the additional compound (E) column, “E-1” represents Silyl SAT10(4,000 in number average molecular weight) manufactured by KanekaCorporation, and “E-2” polypropylene glycol (5,000 in number averagemolecular weight).

1-15. (canceled)
 16. A pressure-sensitive adhesive layer-attachedpolarizing film, comprising: a polarizing film; and a pressure-sensitiveadhesive layer provided on the polarizing film, wherein the polarizingfilm includes a polarizer and a transparent protective film provided ononly one side of the polarizer, the pressure-sensitive adhesive layer isprovided on a side of the polarizer where the transparent protectivefilm is absent, the pressure-sensitive adhesive layer is made of apressure-sensitive adhesive composition containing a (meth)acryl-basedpolymer (A) and an alkali metal salt (B), and an amount of change AP (%)of the pressure-sensitive adhesive layer-attached polarizing film is0.05 or less, AP being a difference between a degree of polarization ofthe pressure-sensitive adhesive layer-attached polarizing film beforestorage at 60° C./95% RH for 500 hours and a degree of polarization ofthe pressure-sensitive adhesive layer-attached polarizing film after thestorage.
 17. The pressure-sensitive adhesive layer-attached polarizingfilm according to claim 16, wherein the alkali metal salt (B) is alithium salt.
 18. The pressure-sensitive adhesive layer-attachedpolarizing film according to claim 16, which comprises 0.0001 to 5 partsby weight of the alkali metal salt (B) based on 100 parts by weight ofthe (meth)acryl-based polymer (A).
 19. The pressure-sensitive adhesivelayer-attached polarizing film according to claim 16, wherein thepolarizer has a thickness of 10 μm or less.
 20. The pressure-sensitiveadhesive layer-attached polarizing film according to claim 19, whereinthe polarizer having a thickness of 10 μm or less is a polarizing layerin the form of a continuous web, and the polarizing layer includes apolyvinyl alcohol-based resin containing an oriented dichroic materialand is a product obtained by a two-stage stretching process includingsubjecting a laminate to auxiliary in-air stretching and subjecting thelaminate to stretching in an aqueous boric acid solution, wherein thelaminate includes a thermoplastic resin substrate and a polyvinylalcohol-based resin layer formed on the substrate.
 21. Thepressure-sensitive adhesive layer-attached polarizing film according toclaim 16, wherein the (meth)acryl-based polymer (A) comprises an alkyl(meth)acrylate monomer unit and a hydroxyl group-containing monomerunit.
 22. The pressure-sensitive adhesive layer-attached polarizing filmaccording to claim 16, wherein the (meth)acryl-based polymer (A)comprises an alkyl (meth)acrylate monomer unit and a carboxylgroup-containing monomer unit.
 23. The pressure-sensitive adhesivelayer-attached polarizing film according to claim 16, further comprisinga crosslinking agent (C).
 24. The pressure-sensitive adhesivelayer-attached polarizing film according to claim 23, which comprises0.01 to 20 parts by weight of the crosslinking agent (C) based on 100parts by weight of the (meth)acryl-based polymer (A).
 25. Thepressure-sensitive adhesive layer-attached polarizing film according toclaim 23, wherein the crosslinking agent (C) is at least one selectedfrom an isocyanate compound and a peroxide.
 26. The pressure-sensitiveadhesive layer-attached polarizing film according to claim 16, furthercomprising 0.001 to 5 parts by weight of a silane coupling agent (D)based on 100 parts by weight of the (meth)acryl-based polymer (A). 27.The pressure-sensitive adhesive layer-attached polarizing film accordingto claim 16, further comprising 0.001 to 10 parts by weight of apolyether-modified silicone compound based on 100 parts by weight of the(meth)acryl-based polymer (A).
 28. The pressure-sensitive adhesivelayer-attached polarizing film according to claim 16, wherein the(meth)acryl-based polymer (A) has a weight average molecular weight of500,000 to 3,000,000.
 29. The pressure-sensitive adhesive layer-attachedpolarizing film according to claim 16, further comprising anadhesion-facilitating layer that is provided between the polarizing filmand the pressure-sensitive adhesive layer.
 30. An image display,comprising at least one piece of the pressure-sensitive adhesivelayer-attached polarizing film according to claim 16.